cavity2: lcavity, tracking_method = runge_kutta, mat6_calc_method = tracking, n_cell = 2, 
rf_frequency = 1.3e9, 
field_calc = fieldmap,
L = 	0.484	, !Grid extends to 0.484. Center of the 2 cells is at 0.286 m 
grid_field = call::cavity2_grid.bmad,
wall = call::cavity2_wall.bmad,
aperture_at = continuous,
aperture_type = wall3d

cavity2[voltage] = 5e6 ! Maximum on-axis Ez in V/m
!CALL, FILE = cavity2_wall.bmad